Instruments and methods for manipulating vertebra

ABSTRACT

A method for manipulating a vertebra includes connecting a first bone anchor to a first vertebra, connecting a second bone anchor to a second bone anchor, positioning a spinal rod in a receiving member of the first bone anchor and in a receiving member of the second bone anchor, connecting a first instrument to the receiving member of the first bone anchor, and manipulating the first instrument to rotate first bone anchor and the first vertebra relative to the second vertebra.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.11/073,352, filed Mar. 4, 2005, the contents of which are incorporatedherein.

BACKGROUND

In spinal deformity surgical procedures, the curvature of the spine, forexample, the coronal curvature and/or the sagittal curvature of thespine, can be corrected by the implantation of a construct of boneanchors (e.g., hooks or bone screws) and spinal fixation elements (e.g.,rods or tethers). In addition to correcting the curvature of the spine,the angular relationship of one or more vertebrae relative to othervertebrae may also be corrected. Conventional surgical procedures forcorrected the angular relationship of a vertebra involve rotating thespinal fixation element, for example, a spinal rod, connected to thevertebra by a bone anchor. In the case of constructs including a spinalrod, this procedure is typically referred to as rod derotation. Rodderotation can place significant stress on the interface between thebone anchors connected to the rotated spinal rod and the vertebra inwhich each bone anchor is implanted. This stress can cause a failure ofone or more of the bone anchors or vertebrae. Accordingly, there is aneed for improved instruments and methods for manipulating, e.g.,rotating a vertebra.

SUMMARY

Disclosed herein are instruments and methods for manipulating avertebra. The instruments and methods disclosed herein are particularlysuited to facilitate rotation of a vertebra relative to another vertebrato correct the angular relationship of the vertebrae.

In accordance with one exemplary embodiment, an instrument formanipulating a vertebra may comprise an inner shaft having a proximalend, a distal end and a lumen extending between the proximal end and thedistal end, a pair of fingers disposed at the distal end of the innershaft, and an outer sleeve disposed about the inner shaft. The innershaft, in the exemplary embodiment, may be movable relative to the outersleeve between a first position in which the fingers are advanced beyonda distal end of the outer sleeve and a second position in which asubstantial portion of the fingers are disposed within the sleeve. Thefingers, when in the first position, may be configured to capture aspinal rod receiving member of the bone anchor therebetween to permitrotation of the bone anchor and a vertebra in which the bone anchor isengaged by manipulation of the instrument.

In accordance with another exemplary embodiment, a system formanipulating one or more vertebra may comprise a first instrument havinga distal end configured to engage a first bone anchor connected to afirst vertebra, a second instrument having a distal end configured toengage a second bone anchor connected to a second vertebra, and aconnector connecting the first instrument and the second instrument. Theconnector, in the exemplary embodiment, may include a first receivingelement for receiving the first instrument and a second receivingelement for receiving the second instrument. The first receiving elementmay be adjustable relative to the second receiving element.

In accordance with another exemplary embodiment, a method formanipulating a vertebra may comprise connecting a first bone anchor to afirst vertebra, connecting a second bone anchor to a second bone anchor,positioning a spinal rod in a receiving member of the first bone anchorand in a receiving member of the second bone anchor, connecting a firstinstrument to the receiving member of the first bone anchor, andmanipulating the first instrument to rotate first bone anchor and thefirst vertebra relative to the second vertebra.

In accordance with another exemplary embodiment, a method formanipulating a vertebra may comprise engaging a first bone anchor to afirst vertebra, the receiving member of the first bone anchor beingadjustable relative to a bone engaging shaft of the first bone anchor ina first direction and restricted from motion in a second direction,connecting a first instrument to the receiving member of the first boneanchor, and moving the first instrument in a direction approximatelyparallel to the second direction to manipulate first bone anchor and thefirst vertebra.

BRIEF DESCRIPTION OF THE FIGURES

These and other features and advantages of the instruments and methodsdisclosed herein will be more fully understood by reference to thefollowing detailed description in conjunction with the attached drawingsin which like reference numerals refer to like elements through thedifferent views. The drawings illustrate principles of the instrumentsand methods disclosed herein and, although not to scale, show relativedimensions.

FIG. 1 is a perspective view of an exemplary embodiment of an instrumentfor manipulating a vertebra, illustrating the instrument in a firstposition for engaging a bone anchor;

FIG. 2 is a perspective view of the distal end of the instrument of FIG.1, illustrating the instrument in the first position for engaging a boneanchor;

FIG. 3 is a perspective view of the distal end of the instrument of FIG.1, illustrating the instrument in a second position;

FIGS. 4A-4C are side elevational views in cross section of theinstrument of FIG. 1, illustrating the instrument in the first position;

FIGS. 5A-5C are side elevational views in cross section of theinstrument of FIG. 1, illustrating the instrument in the secondposition;

FIG. 6 is a side elevational view in cross section of the distal end ofthe instrument of FIG. 1 taken along the line A-A of FIG. 4B;

FIG. 7 is a perspective view of a connector for connecting twoinstruments, such as the instrument of FIG. 1, illustrating theconnector in an open position;

FIG. 8 is a partial cut away side view of the connector of FIG. 7,illustrating the connector in an open position;

FIG. 9 is a perspective view of the connector of FIG. 7, illustratingthe connector in the closed position and connecting two instruments suchas the instrument of FIG. 1;

FIG. 10 is a perspective view of the connector of FIG. 7, illustratingthe connector in the closed position and connecting two instruments suchas the instrument of FIG. 1;

FIG. 11 is a perspective view of a first instrument connected to a firstbone anchor engaged to a first vertebra and a second instrumentconnected to a second bone anchor engaged to a second vertebra,illustrating a method of adjusting the first vertebra relative to thesecond vertebra;

FIGS. 12 and 13 are perspective views of a connector connecting a firstinstrument to a second instrument, illustrating a method of adjusting afirst and third vertebra relative to a second vertebra;

FIG. 14 is an exploded perspective view of the receiving member of abone anchor in which the receiving member is adjustable relative to thebone engaging shaft of the bone anchor in a first direction andrestricted from motion in a second direction;

FIG. 15 is a side elevation view of the bone anchor of FIG. 14;

FIG. 16 is a side elevation view in cross section of the bone anchor ofFIG. 14, taken along the line B-B of FIG. 15; and

FIGS. 17A and 17B are perspective views of an exemplary embodiment of aninstrument for manipulating a vertebra, illustrating the instrument in afirst position for capturing a bone anchor (FIG. 17A) and a secondposition for retaining the bone anchor (FIG. 17B).

DETAIL DESCRIPTION OF EXEMPLARY EMBODIMENTS

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the instruments and methods disclosed herein.One or more examples of these embodiments are illustrated in theaccompanying drawings. Those of ordinary skill in the art willunderstand that the instruments and methods specifically describedherein and illustrated in the accompanying drawings are non-limitingexemplary embodiments and that the scope of the present invention isdefined solely by the claims. The features illustrated or described inconnection with one exemplary embodiment may be combined with thefeatures of other embodiments. Such modifications and variations areintended to be included within the scope of the present invention.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e. to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

The terms “comprise,” “include,” and “have,” and the derivativesthereof, are used herein interchangeably as comprehensive, open-endedterms. For example, use of “comprising,” “including,” or “having” meansthat whatever element is comprised, had, or included, is not the onlyelement encompassed by the subject of the clause that contains the verb.

FIGS. 1-6 illustrate an exemplary embodiment of an instrument 10 formanipulating a vertebra. The exemplary instrument 10 includes an innershaft 12, an implant engagement mechanism 14 disposed at the distal end18 of the inner shaft 12, and an outer sleeve 16 disposed about theinner shaft 12. The exemplary instrument 10 may be employed to engage abone anchor 60 implanted in a vertebra and maneuver the bone anchor 60and the vertebra by manipulating the instrument 10. For example, theexemplary instrument 10 may be employed to rotate the bone anchor 60 andthe vertebra relative to other vertebrae and thereby by correct theangular orientation of the vertebra. The instrument 10, when employed inthe exemplary manner, thus may be used to effect segmental correction ofthe angular orientation of the vertebrae of the spine.

The inner shaft 12 of the exemplary instrument 10 may have a distal end18, a proximal end 20, and a lumen 22 extending between the proximal end20 and the distal end 18. In the exemplary embodiment, the inner shaft12 is generally tubular in shape having an approximately circular crosssection. One skilled in the art will appreciate that the inner shaft 12may have other cross sectional shapes including elliptical orrectilinear. The lumen 22 of the inner shaft 12 may be sized to receivean instrument, such as a screw driver or the like, therethrough. Theouter sleeve 16 of the exemplary instrument 10 is disposed about theinner shaft 12 and may have a distal end 24, a proximal end 26, and alumen 28 extending between the proximal end 26 and the distal end 24.The outer sleeve 16 and the inner shaft 12 may have complementary shapesto facilitate positioning of the inner shaft 12 within the outer sleeve16. For example, in the illustrated embodiment, the outer sleeve isgenerally tubular in shape have an approximately circular cross sectionand the longitudinal axis of the elongate shaft 12 is coincident withthe longitudinal axis of the outer sleeve 16. The inner shaft 12 may bedisposed within the lumen 28 of the outer sleeve 16 and may be movablewithin the lumen 28 relative to the outer sleeve 16. For example, theinner shaft 12 may be movable along the longitudinal axis of the outersleeve 16.

The proximal end 20 of the inner shaft 12 may include a mechanism toretain the inner shaft 12 in a position relative to the outer sleeve 16.For example, in the exemplary embodiment, an annular ridge 30 may beprovided proximate the proximal end 20 of the inner shaft 12 or at otherlocations along the length of the shaft 12. The annular ridge 30 may bean increased diameter segment of the shaft 12 that is sized, shaped, andpositioned to engage a shoulder 32 provided within the lumen 28 of theouter sleeve 16 and maintain the inner shaft 12 in a predeterminedposition relative to the outer sleeve 16. The shoulder 32 may be annularin shape and may be defined by a narrowing of the inner diameter of thelumen 28 of the sleeve 16. The shoulder 32 may have a sloped outersurface to minimize the effect of wear on the shoulder 32. In theexemplary embodiment, the annular ridge 30 may be selectively engagedand disengaged to permit the inner shaft 12 to be selectively movedrelative to the outer sleeve 16. For example, the proximal end 20 of theinner shaft 12 may be moved between an increased diameter configuration,in which the ridge 30 engages the shoulder 32 to maintain the innershaft 12 in position relative to the outer sleeve 16, as illustrated inFIGS. 4A-C, and a decreased diameter configuration, in which the ridge30 disengages the shoulder 32 to permit the inner shaft 12 to moverelative to the outer sleeve 16, as illustrated in FIGS. 5A-C. In theexemplary embodiment, the proximal end 20 of the inner shaft 12 isgenerally U-shaped in cross section having a pair of tabs 34A, 34Bspaced apart by a slot 36. The tabs 34A, 34B may be compressed towardone another to facilitate movement of the proximal end 28 of the innershaft 12 from the increase diameter configuration to the decreaseddiameter configuration. The tabs 34A, 34B may be biased to the increaseddiameter configuration in which the tabs 34A, 34B are positionedgenerally parallel to one another.

The exemplary instrument 10 may include a plunger 40 positioned withinthe outer sleeve 16 at the proximal end 26 of the outer sleeve 16. Theplunger 40, in the exemplary embodiment, is engageable with the proximalend 20 of the inner shaft 12 and is operable to move inner shaft 12relative to the outer sleeve 16. In the exemplary embodiment, theplunger 40 may have a distal end 42 configured to move the proximal end20 of the inner shaft 12 from the increased diameter configuration tothe decreased diameter configuration. For example, the distal end 42 ofthe plunger 40 may be generally cylindrical in shape and may have aninner diameter less than the diameter of the annular ridge 30. Inoperation, the plunger 40 may be advanced from a proximal position,illustrated in FIGS. 4A-C, to a distal position in which the distal end42 is advanced about the proximal end 20 of the inner shaft 12 to engagethe annular ridge 30 and compress the tabs 34A, 34B towards one another.The annular ridge 30 may have a sloped outer surface to facilitateengagement with the proximal end 42 of the plunger 40 and translation ofthe proximal end 28 from the increased diameter configuration to thedecreased diameter configuration. The instrument 10 may include aproximal spring 44 positioned between the outer sleeve 12 and theplunger 40 to bias the plunger 40 to a proximal position.

One skilled in the art will appreciate that other mechanisms for movingthe inner shaft 12 relative to the outer sleeve 16 may be employed. Forexample, the outer sleeve 16 may include external threads for connectingwith an internally threaded collar. The collar may engage the innershaft to advance and/or retract the inner shaft 12 by rotation of thecollar about the outer sleeve 16.

The exemplary instrument 10 includes an implant engagement mechanism 14configured to engage a bone anchor 60, such as, for example, a hook, amonoaxial bone screw, or a polyaxial bone screw, and thereby by connectthe instrument to the bone anchor 60 in a manner sufficient to permitmanipulation of the bone anchor and the vertebra in which the boneanchor is implanted. In the exemplary embodiment, the implant engagementmechanism 14 is a pair of fingers 50A, B at the distal end 18 of theinner shaft 12. In the exemplary embodiment, the fingers 50A and 5OB aredefined by the sidewalls of the inner tube 12 and are separated by slots52A and 52B. In certain exemplary embodiments, fingers 50A and 50B maybe flexible and resilient in the radial direction to facilitateconnection to a bone anchor. For example, the fingers 50A and 50B may beflexed apart in the radial direction from a first, relaxed position tofacilitate advancement of the fingers longitudinally over a portion ofthe bone anchor. Once positioned about a portion of the bone anchor, thefingers 50A and 50B may provide a radially compressive force on the boneanchor as the fingers 50A and 50B attempt to return to the first,relaxed position. In other exemplary embodiments, including theexemplary instrument 10, the fingers 50A and 50B need not be flexibleand resilient.

The inner shaft 12, in the exemplary embodiment, may be movable relativeto the outer sleeve 16 between a first, distal position in which thefingers 50A, 50B are advanced beyond a distal end 24 of the outer sleeve16, as illustrated in FIGS. 1, 2, and 4A-4C, and a second, proximalposition in which a substantial portion of the fingers 50A, B aredisposed within the sleeve 16, as illustrated in FIGS. 3 and 5A-C. Thefingers 50A, 50C, when the inner shaft 12 is in the first position, maybe configured to capture the bone anchor 60 therebetween. In theexemplary embodiment, for example, fingers 50A, 50B may move apart fromone another when the inner shaft 12 is moved to the first position tofacilitate positioning of the spinal rod receiving member 62 of the boneanchor 60, between the fingers 50A, 50B.

The fingers 50A, B, when the inner shaft 12 is moved to the second,proximal position, may move toward one another to retain the bone anchor60 between the fingers 50A, 50B. The fingers 50A, 50B may be inhibitedfrom separating by the outer sleeve 16 when the inner shaft is in thesecond, proximal position. The fingers 50A, 50B, when the inner shaft isin the second, proximal position are spaced apart a distance sufficientto retain the bone anchor between the fingers 50A, 50B. In the exemplaryembodiment, for example, the bone anchor 60 is retained between thefingers 50A, 50B in a manner sufficient to permit maneuvering of thebone anchor and a vertebra in which the bone anchor is implanted bymanipulation of the instrument. For example, the bone anchor 60 andvertebra may be rotated, moved along the axis of the instrument 10,and/or moved in a direction perpendicular to the axis to the instrument10 by the instrument 10.

In the illustrated exemplary embodiment, each finger 50A and 50B mayinclude one or more radially inward facing projection 54A, 54B that issized and shaped to seat within an opening provided in a portion of thebone anchor to facilitate retention of the bone anchor 60 by the fingers50A, 50B. The size, shape and number of projections can be varieddepending on, for example, the opening(s) provided on the bone anchorand type of connection desired. In the illustrated exemplary embodiment,for example, each projection 54A, 54B is generally arcuate in shape andhas a cross section that is complementary to an arcuate groove 64provided in the spinal fixation element receiving member 62 of theexemplary bone anchor 60. An exemplary bone anchor having an arcuategroove to facilitate connection with an instrument is described indetail in U.S. patent application Ser. No. 10/738,286, filed Dec. 16,2003, incorporated herein by reference.

In the exemplary embodiment, the outer sleeve 16 of the instrument 10may include one or more projections 70 on the inner surface thereof. Theprojections 70 may be positioned at the distal end 24 of the outersleeve 16 to facilitate separation of the fingers 50A, 50B as innershaft 12, and, thus, the fingers 50A, 50B are moved to the first, distalposition. In the exemplary embodiment, a pair of cylindrical shapedprojections 70 are spaced diametrically opposed to one another at thedistal end 24 of the outer sleeve 16. The projections 70A, 70B, in theexemplary embodiment, are positioned within the slots 52A, 52B,respectively. The slots 52A, 52B narrow in the proximal direction.Advancement of the projections 70A, 70B within the slots 52A, 52B causesthe fingers 50A, 50B to separate.

In alternative exemplary embodiments, the projections 70A, 70B may notbe provided. In such embodiments, the fingers 50A, 50B may remainapproximately parallel to one another when the inner shaft 12 is advanceto the first position. The fingers 50A, 50B may be rotated intoengagement with the bone anchor by, for example, positioning the fingers50A, 50B in the rod slots of the receiving member 62 of the bone anchor60 and rotating the fingers 50A, 50B such that the projections 54A, 54Beach engage a groove 64. Alternatively, the fingers 50A, 50B may beflexed apart as the fingers 50A, 50B engage the receiving member 62 and,as the inner shaft 12 is advanced distally relative to the receivingmember 62, each projection 54A, 54B may snap into engagement with agroove 64.

The instrument 10 may include one or more springs to bias the innershaft 12 to the first position or the second position. In the exemplaryembodiment, for example, a distal spring 75 may engage the inner shaft12 and the outer sleeve 16 to bias the inner shaft 12 to the first,distal position.

The exemplary instrument 10 may include a connection element configureto engage a connector, such as the exemplary connector 200 describedbelow, for connecting the instrument 10 to another instrument, forexample, another instrument for manipulating a vertebra. In theillustrated exemplary embodiment, for example the outer sleeve 16includes a connection element 80 positioned at the proximal end 26 ofthe outer sleeve 16. The connection element 80 may be configured topermit polyaxial motion of the instrument 10 relative to the connector.For example, the connection element 80 of the exemplary embodiment mayhave be at least partially spherical in shape to engage a complementaryshaped receiving element of the connector.

The exemplary instrument 10 may be constructed of any biocompatiblematerial including, for example, metals, such as stainless steel ortitanium, polymers, ceramics, or composites thereof. The length anddiameter of the instrument 10 may vary depending on the area of thespine being treated (e.g., lumbar, thoracic, or cervical) and theapproach (e.g., posterior, anterior, or lateral). For example, thelength of the instrument 10 may be selected to at least span from a skinincision to proximate a vertebra. The diameter of the instrument 10 maybe selected to facilitate positioning of the instrument 10 through anopen incision or a minimally invasive incision. In certain exemplaryembodiments, for example, the diameter of the instrument may be selectedto facilitate delivery of the instrument 10 through a minimally invasiveaccess device such as a cannula or expandable retractor.

FIGS. 7-10 illustrate an exemplary embodiment of a connector 200 forconnecting two or more instruments and facilitating cooperative movementof the instruments. The exemplary connector 200 is particularly suitedto connecting one or more instruments for manipulating a vertebra, suchas the instrument 10 described above. One skilled in the art willappreciate, however, the connector 200 may be used to connect any typeof spinal or surgical instruments.

The exemplary connector 200 may include a plurality of receivingelements 202, each of which connects to an instrument. Any number of thereceiving elements 202 may be provided. In the illustrated exemplaryembodiment, the connector 200 includes a first adjustable receivingelement 202A for receiving a first instrument and a second receivingelement 202B for receiving a second instrument. The first receivingelement 202A and/or the second receiving element 202B may be adjustablerelative to one another to facilitate connection to two spaced apartinstruments. For example, in the illustrated exemplary embodiment, thefirst receiving element 202A is adjustable relative to the secondreceiving element 202B and the connector 200 and the second receivingelement 202B is fixed relative to the connector 200.

The exemplary connector 200 may include a first arm 204 pivotablyconnected to second arm 206 at a pivot point defined by a hinge pin 208.The exemplary connector 200 may be movable between an open position inwhich the first end 210 of the first arm 204 is separated from the firstend 212 of the second arm 206, as illustrated in FIGS. 7 and 8, and aclosed position in which the first end 210 of the first arm 204 iscoupled to the first end 212 of the second arm 206, as illustrated inFIGS. 9 and 10. The open position facilitates connection of theinstruments to the receiving elements 202 and adjustment of anadjustable receiving element, such receiving element 202A. The exemplaryconnector 200 may include a latch mechanism 214 for selective couplingthe first end 210 of the first arm 204 to the first end 212 of thesecond arm 206. In the exemplary embodiment, the latch mechanism 214 mayinclude hook 220 positioned on the first arm 204 that may selectivelyengage a hook retaining element 222 positioned on the second arm 206. Acylindrically-shaped push button 226 is connected to the hook 222.Movement of the push button in a direction toward the hinge 208 causesthe hook 220 to disengage from the hook retaining element 222 and, thus,releases the first arm 204 from the second arm 206. A spring 228 biasesthe push button 226 in a direction away from the hinge 208 and, thus,biases the hook 208 into an engagement position. The outer surface 228of the hook 220 may be curved or angled to provide a camming surfacethat, when engaged by the bottom surface of the hook retaining element222, causes the hook 220 to move from the engagement position toward thehinge 208, thus, allowing the hook 220 to engage the hook retainingelement 222.

The first and/or second arm 204/206 may include a retaining member forretaining the adjustable receiving elements 202 on the arms when theconnector is in the open position. For example, the second arm 206 ofthe exemplary connector 200 includes a retaining pin 225 for retainingthe first receiving element 202A on the second arm 206. The retainingpin 225 may be adjusted along it is axis between an extended position inwhich the pin 225 impedes motion of the receiving element along the arm206 and retracted position that facilitates removal and placement of thereceiving element 202 on the arm 206. A spring 227 may be provided tobias the pin 225 to the extended position.

The first receiving element 202A, in the exemplary embodiment, includesa slot 232 for receiving the second arm 206 and permitting motion of thefirst receiving element 202A relative to the second arm 206 and otherreceiving elements, such as the second receiving element 202B. In theexemplary embodiment, the first arm 204 includes a plurality of teeth230 for engaging a plurality of teeth on one or more of the receivingelements, for example, the first receiving element 202A, when theconnector 200 is in the closed position. The engagement of the teeth 230with teeth provided on an adjustable receiving element, for example, theadjustable receiving element 202A, may inhibit motion of the adjustablereceiving element, thereby fixing the adjustable receiving element inposition relative to the first arm 204, the second arm 206, and theother receiving elements.

The first receiving element 202A is generally C-shaped having an opening234 to facilitate positioning of an instrument within the receivingelement 202A. The first arm 204 may be positioned across the opening 234when the connector is in the closed position to retain the instrument inthe first receiving element 202A. The first receiving element 202A maybe configured to permit polyaxial motion of an instrument relative tothe receiving element 202A and, thus, the connector 200. For example,the first receiving element 202A may include a partially sphericallyshaped surface 236 that defines a seat or engagement surface for theconnection element of the instrument, for example, the partiallyspherically shaped connection element 80 of the exemplary instrument 10,described above. The instrument 10, when connected to the firstreceiving element 202A of the connector 200, may be moved in a pluralityof directions, for example, perpendicular to, parallel to, and about theaxis of the instrument 10, as illustrated in FIGS. 9 and 10.

The second receiving element 202B, in the exemplary embodiment, may bedefined by a first arcuate surface 240A provided on the first arm 204and a second arcuate surface 240B provided on the second arm 206. Thefirst arcuate surface 240A may be spaced apart from the second arcuatesurface 240B when the connector 200 is in the open position, asillustrated in FIGS. 7 and 8, to facilitate positioning of an instrumentwithin the second receiving element 202B. When the connector 200 is inthe closed position, as illustrated in FIGS. 9 and 10, the first arcuatesurface 240A and the second arcuate surface 240B are spaced apart adistance sufficient to retain the instrument within the second receivingelement 202B. The second receiving element 202B, like the firstreceiving element 202A, may be configured to permit polyaxial motion ofan instrument relative to the receiving element 202B and, thus, theconnector 200. For example, the first arcuate surface 240A and thesecond arcuate surface 240B may each have a partially spherically shapedsurface 242A, 242B that cooperatively define a seat or engagementsurface for the connection element of the instrument, for example, thepartially spherically shaped connection element 80 of the exemplaryinstrument 10, described above. The instrument 10, when connected to thesecond receiving element 202B of the connector 200, may be moved in aplurality of directions, for example, perpendicular to, parallel to, andabout the axis of the instrument 10, as illustrated in FIGS. 9 and 10.

While the exemplary embodiment of the connector 200 is described andillustrated as having two receiving elements, the number and type (i.e.,fixed or adjustable) of receiving elements may be varied to accommodatethe number of instruments desired to be connected. For example, theexemplary connector 200 illustrated in FIGS. 12 and 13 includes threereceiving elements—a fixed receiving element and two adjustablereceiving elements.

The exemplary instrument 10 may be employed to manipulate a bone anchorand the vertebra in which the bone anchor is implanted. In one exemplarymethod of manipulating a vertebra, the instrument 10 may be coupled tothe receiving member or other portion of a bone anchor. Referring toFIG. 11, for example, a first instrument 10A may be coupled to thereceiving member 62 of a bone anchor 60.

In the exemplary method, a spinal construct including a plurality ofbone anchors implanted in a plurality of vertebra and a spinal rodconnecting the bone anchors may be positioned in advance of using thefirst instrument to manipulate a vertebra. For example, a first boneanchor 60A may be connected to a first vertebra VB1, a second boneanchor 60B may be connected to a second vertebra VB2, a third boneanchor 60C may be connected to a third vertebra VB3, and a fourthvertebra 60D may be connected to a fourth vertebra VB4. In the exemplarymethod, the first, second, third, and fourth vertebrae are adjacent oneanother. In other exemplary methods, the bone anchors may be connectedto non-adjacent vertebra to create the spinal construct. The boneanchors may be implanted into any suitable portion of the vertebrae. Inthe exemplary method, for example, each bone anchor is implanted into apedicle of the vertebra.

A spinal rod 90A may be positioned relative to the bone anchors. Forexample, the spinal rod may be positioned in the receiving member 62 ofeach bone anchor 60. In the exemplary method, a closure mechanism, suchas, for example, an inner set screw 68 may be positioned in thereceiving member 62 of the bone anchors 60 to retain the spinal rodrelative to the bone anchor.

In certain exemplary embodiments, a second construct may be positionedon the contra-lateral side of the spine from the first construct. In theexemplary method, a fifth bone anchor 60E is connected to the firstvertebra VB1 opposite the first bone anchor 60A, a sixth bone anchor 60Fis connected to the second vertebra VB2 opposite the second bone anchor60B, a seventh bone anchor 60F is connected to the third vertebra VB3opposite the third bone anchor 60C, and an eighth bone anchor 60G isconnected to the fourth vertebra VB4 opposite the fourth bone anchor60D. A second spinal rod 90B may be connected to the bone anchors 60E-G.

One skilled in the art will appreciate that the constructs illustratedin the FIGURES are exemplary constructs for facilitating the descriptionof the use of the instruments and methods described herein. Otherconstructs employing the same or different bone anchors and fixationelements may be employed without departing from the scope of the presentinvention.

After connecting the first instrument 10A, the first instrument 10A maybe manipulated to maneuver the second bone anchor 60B and the secondvertebra VB2 relative to the first vertebra VB1, third vertebra VB3, andthe fourth vertebra VB4. For example, the first instrument l0A may bemoved a direction about the axis A of the spine, as indicated by arrow Rin FIG. 11, to rotate the second vertebra VB2 about the axis A of thespine. Moreover, the instrument 10 may be used to maneuver the secondbone anchor 60B and the second vertebra VB2 in any direction.

In the exemplary method, a second instrument 110B may be connected tothe fifth bone anchor 60E, which is connected to the first vertebra VB1.The second instrument 10B and the first instrument 10A may bemanipulated to maneuver the first vertebra VB1 and the second vertebraVB2 relative to one another. For example, the first instrument 10A maybe rotated about the axis A of the spine to rotate the second vertebraVB2 about the spine and the second instrument 10B may be rotated aboutthe axis A of the spine to rotate the first vertebra VB1 about the axisA of the spine. The first instrument 10A and the second instrument 10Bmay provide counter-torque to one another to facilitate motion of thefirst and second vertebrae. For example, the first instrument 10A andthe second instrument 10B may be rotated in opposite directions aboutthe axis A of the spine to facilitate correction of the angularorientation of the second vertebra VB2 and the first vertebra VB1.

In the exemplary method, a driver instrument may be inserted through thelumen 22 of the inner shaft 12 of the first instrument 10 to effecttightening of the closure mechanism 68B of the second bone anchor 60B.For example, a screw driver or the like may be advanced into engagementwith the set screw of the bone anchor and may be manipulated to tightenthe set screw to restrict motion of the spinal rod 90A relative to boneanchor 60B. In the exemplary method, the closure mechanism may betightened after the angular orientation/position of the vertebra isadjusted by the first instrument 10A.

FIGS. 12 and 13 illustrate an exemplary method for manipulating aplurality of vertebrae. In the exemplary method, a first instrument 1OAmay be connected to a bone anchor 60B connected to a second vertebra. Inaddition, a second instrument 10B may be connected to a bone anchor 60Econnected to a first vertebra and a third instrument 10C may beconnected to a bone anchor 60H connected to a fourth vertebra VB4. Thesecond and third instruments 10B, 10C may be connected by a connector,such as the connector 200 described above. After connecting the secondand third instruments 10B, 10C to the respective bone anchor, the firstreceiving element 202A may be adjusted relative to the second receivingelement 202B to facilitate connection of the second instrument 10B tothe first receiving element 202A and the third instrument 10B to thesecond receiving element 202B. The connector 200 may be moved tomanipulate the second instrument 10B and the third instrument 10C torotate the first vertebra VB1 and the fourth vertebra VB4 relative toone another. For example, the connector 200 may be rotated in adirection indicated by arrow R about the axis A to rotate the firstvertebra VB1 and the fourth vertebra VB2 about the axis A of the spineand relative to the second vertebra VB2 and the third vertebra VB3.Moreover, the first instrument 10A may be rotated in cooperation withthe connector 200 to rotate the second vertebra VB2 about the axis A ofthe spine. The connector 200, and the second instrument 10B and thirdinstrument 10C connected thereto, and the first instrument 10B mayprovide counter torque to one another. For example, the connector 200and the first instrument 10A may be rotated in opposite directions aboutthe axis A of the spine to facilitate correction of the angularorientation of the first vertebra VB1, the second vertebra VB2, and thefourth vertebra VB4.

The exemplary instruments described here in may be used with any type ofbone anchor including, for example, a monoaxial bone screw, a polyaxialscrew, or a hook. FIGS. 14-16 illustrates an exemplary embodiment of abone screw 100 having a receiving member 140 that is adjustable relativeto the bone engaging shaft 114 of the bone anchor 100 in a firstdirection and restricted from motion in a second direction. Acompression and restriction member 180 for seating the head 116 of thebone engaging shaft 114 within the rod receiving member 140 includesrestriction protrusions 192, 194 or other suitable mechanisms forselectively limiting the movement of the bone engaging shaft 114relative to the receiving member 140. Such a bone anchor is described indetail in U.S. patent application Ser. No. ______, filed concurrentlyherewith, entitled Constrained motion Screw Assembly (Attorney DocketNo. DUQ-006), incorporated herein by reference.

The bone engaging shaft 114 may include one or more bone engagementmechanisms, such as, for example, an external thread 118. The receivingmember 140 receives the proximal head 116 of the bone anchor to couplethe bone anchor 114 thereto, thereby coupling the bone to a rod or otherelement received in the rod-receiving member 140. In a rest position,the longitudinal axis 122 of the bone anchor aligns with a longitudinalaxis 142 extending through the receiving member 140. The bone engagingshaft 114 is pivotable relative to the receiving member 140 about theproximal head 116 in one or more selected directions to angulate thelongitudinal axis 122 relative to the longitudinal axis 142. The boneanchor 100 further includes one or more components, illustrated as thecompression and restriction member 180, for preventing a pivotingmovement of the bone engaging shaft 114 in one or more directions, sothat the bone engaging shaft 114 cannot pivot in all 360 degrees aroundthe receiving member 140, thereby increasing the stability of the screwassembly in one or more planes. For example, referring to FIGS. 15 and16, the shaft is pivotable about axis T-T, but constrained from pivotingabout axis R-R. Axis R-R is aligned with and parallel to thelongitudinal axis r-r of the rod 12 in a selected plane andperpendicular to axis T-T, intersecting T-T at pivot point P, and may besubstantially parallel to the longitudinal axis r-r of a rod to bereceived in the receiving portion 140.

The anchor head 116 of the bone engaging shaft 114 may be configured tofacilitate controlled adjustment of the bone engaging shaft 114 relativeto the receiving member 140 of the bone screw assembly. For example, theillustrative anchor head 116 may be substantially spherical and includecurved side surfaces 161, 162 that are shaped to permit pivoting of thebone engaging shaft 114 relative to the receiving member 140 in one ormore selected directions. The curved side surfaces 161, 162 arepreferably curved in three-dimensions to facilitate rotation of the boneengaging shaft 114 relative to the receiving member 140. Theillustrative anchor head 116 further includes two opposed flat sidesurfaces 163, 165 for constraining the pivoting movement to the one ormore selected directions. The flat surfaces 163, 165 preferably extendsubstantially parallel to the longitudinal axis 122 of the shaft 114.While the illustrative embodiment shows two opposed flat side surfaces163, 165, one skilled in the art will recognize that the head can haveany suitable number of flat surfaces or other selected feature forlimiting the path of the shaft 114 relative to the receiving portion 140about any selected axis or axes. The top surface 167 of the anchor head116 may be a generally planar surface to facilitate seating of theanchor within the rod-receiving portion 140 of the screw assembly. Theanchor head 116 may also have surface texturing, knurling and/or ridges.

The illustrative bone screw 100 further includes a compression andrestriction member 180 for seating the anchor head 116 within therod-receiving portion 140 of the screw 100 and for cooperating with theflat surfaces 163, 165 to constrain the movement of the anchor portionrelative to the rod-receiving portion 140. The compression andrestriction member 180 preferably forms a proximal rod seat 182 forseating a rod or other spinal fixation element and an opposed distalanchor seat 197 for engaging the anchor head 116. The illustrativecompression and restriction member 180 includes a cap 181 andrestricting protrusions 192, 194 that extend from a lower surface 184 ofthe cap 181. The restricting protrusions 192, 194 form a track-likeregion 197 for receiving the anchor head 116 therebetween. Therestricting protrusions 192, 194 are configured to mate with the flatsurfaces 163, 165 of the anchor head 116 when the bone screw 100 isassembled to guide and constrain the pivoting movement of the anchorhead 116 relative to the receiving member 140. The illustrativerestricting protrusions 192, 194 restrict movement of the anchor head116 about axis T-T through a plane that is parallel to the flat faces163, 165 of the proximal head 116 and the protrusions 192, 194.

In illustrative embodiment, the plane through which the bone engagingshaft 114 pivots is preferably defined by the longitudinal axis r-r of arod inserted in the receiving member 140 when the bone screw 100 isassembled and the longitudinal axis 142 of the receiving member 142.However, one skilled in the art will recognize that the screw 100 mayalso be made to pivot in one or more other directions relative to therod-receiving member 140.

The illustrated bone screw 100 facilitates positioning of the spinal rod12 relative to the receiver member 140 by permitting the receiver member140 to pivot relative to the shaft 114 about axis T-T, (e.g., thereceiver member 140 is movable in the sagittal plane). Moreover, theillustrated bone screw 100 facilitates adjustment of the angularorientation of the vertebra in which the bone screw is implanted by aninstrument connected to the bone anchor 100, such as the exemplaryinstrument 10 described above. For example, the bone screw 100 providesstability in the transverse plane by restricting pivoting of thereceiver member 140 about the axis R-R. The stability of the bone screwin the transverse plane facilitates movement of the bone screw 100 andvertebra in the transverse plane, e.g., facilitates rotation of the boneanchor 100 and the vertebra about axis R-R.

FIG. 17A & 17B illustrate an alternative embodiment of an instrument 210for manipulating a vertebra. The exemplary instrument 210 includes anelongate shaft 212 including a pair of fingers 250A, 250B positioned atthe distal end of the shaft 212. A first finger 250A is movable relativeto a second finger 50B to allow the fingers 250A, 250B to capture aportion of a bone anchor 60 there-between. In the exemplary embodiment,for example, the first finger 250A may be pivotably connected by a hinge251 to the shaft 212 and the second finger 250B is integral to the shaft212. The first finger 250A is movable between a first position,illustrated in FIG. 17A, in which the first finger 250A is spaced apartfrom the second finger 250B to allow the fingers 250A, 250B to receive aportion of a bone anchor 60 there-between, and a second position,illustrated in FIG. 17B, in which the first finger 250A is proximate thesecond FIG. 250B to retain the portion of bone anchor between thefingers 250A,B.

A lever arm 261 or other actuation mechanism may be coupled to the firstfinger 250A to facilitate movement of the first finger 250A between thefirst and second position. The lever arm 261, in the exemplaryembodiment, is coupled to the first finger 250A through a plurality ofpivot points, e.g. hinges 251, 253, 258. The lever arm 261 may be movedtowards or away from the shaft 212 to move the first finger 250A betweenthe first and second positions. A leaf spring 263, or other spring, maybe provided to bias the lever arm 261 away from the shaft 212, asillustrated in FIG. 17A. A latch 265 may be provided at the proximal endof the shaft 212 to selectively retain the lever arm 261 in contact withthe shaft 212, as illustrated in FIG. 17B.

While the instruments and methods of the present invention have beenparticularly shown and described with reference to the exemplaryembodiments thereof, those of ordinary skill in the art will understandthat various changes may be made in the form and details herein withoutdeparting from the spirit and scope of the present invention. Those ofordinary skill in the art will recognize or be able to ascertain manyequivalents to the exemplary embodiments described specifically hereinby using no more than routine experimentation. Such equivalents areintended to be encompassed by the scope of the present invention and theappended claims.

1. An instrument for manipulating a vertebra, the instrument comprising:an inner shaft having a proximal end, a distal end and a lumen extendingbetween the proximal end and the distal end, a pair of fingers disposedat the distal end of the inner shaft, and an outer sleeve disposed aboutthe inner shaft, the inner shaft movable relative to the outer sleevebetween a first position in which the fingers are advanced beyond adistal end of the outer sleeve and a second position in which asubstantial portion of the fingers are disposed within the sleeve, thefingers, when in the first position, configured to capture a spinal rodreceiving member of the bone anchor therebetween, the fingers, when inthe second position, configured to retain the spinal rod receivingmember of the bone anchor therebetween to permit rotation of the boneanchor and a vertebra in which the bone anchor is engaged bymanipulation of the instrument.
 2. The instrument of claim 1, whereinthe outer sleeve includes a connection element configured to engage aconnector for connecting the instrument to another instrument.
 3. Theinstrument of claim 2, wherein the connection element is configured topermit polyaxial motion of the instrument relative to the connector. 4.The instrument of claim 3, wherein the connection element is at leastpartially spherical in shape.
 5. The instrument of claim 1, wherein thefingers separate when moved to the first position.
 6. The instrument ofclaim 5, wherein the outer sleeve includes a projection on an surfacethereof, the projection positioned at the distal end of the outer sleeveto facilitate separation of the fingers as the fingers are moved to thefirst position.
 7. The instrument of claim 1, further comprising aplunger positioned within the outer sleeve at a proximal end of theouter sleeve, the plunger engageable with the inner shaft and operableto move the fingers to the first position.
 8. The instrument of claim 1,further comprising a spring connected to the inner shaft and the outersleeve, the spring biasing the fingers to the first position.